This invention is related to microfinishing tooling particularly adapted for microfinishing irregular surfaces such as cam lobes for internal combustion engine camshafts.
Numerous types of machinery components must have finely controlled surface finishes in order to perform satisfactorily. For example, surface finish control, also referred to as "microfinishing" is particularly significant in relation to the manufacturing of journal bearings and cam surfaces such as are found on internal combustion engine crankshafts, camshafts and power transmission shafts. When microfinishing surfaces which are cylindrical in shape, an insert having a surface conforming to the workpiece is used which presses an abrasive coated film against the surface as the tooling or the workpiece is rotated. The relative sliding motion of the workpiece surface along the abrasive film causes the surface finish to be improved by abrasive action. For surfaces which are not surfaces of revolution or which are rotated about an axis offset from their center such as cam surfaces, tooling capable of following the workpiece surface during roation is required. Microfinishing operations for surfaces such as the cam lobes on internal combustion engine camshafts are typically carried out using an insert made of a relatively hard but compressible material such as urethane which presses the machining film against the cam surface Such insert typically have "fingers" which are resilient to maintain the film in continuous contact with the workpiece surface. Although prior art devices for accomplishing such microfinishing of irregular surfaces like cam lobes operate generally satisfactorily, they suffer from a number of drawbacks. When using a solid insert material such as urethane, periodic indexing of the abrasive coated film needed to present a new abrasive surface for microfinishing between machining cycles causes wear of the insert. In addition, a minute amount of movement occurs between the insert and film during microfinishing causing a "scrubbing" action which wears the insert. Another disadvantage of such tooling is deformation of the tooling as it follows the contours of a cam surface as it is rotated causing uneven and non-uniform pressure to be applied to the workpiece surface.
This invention is directed toward improved microfinishing tooling particularly adapted for microfinishing irregular surfaces such as camshaft lobes. The tooling utilizes a pair of rollers which press an abrasive coated film against the workpiece during microfinishing. The rollers are free to rotate when the abrasive coated film is indexed and during microfinishing to minimize wearing of the roller surfaces. Moreover, since the rollers are made from a hard material, they are not subject to rapid wear due to the film indexing motion. The roller shoes are further provided with articulating pivots which enable the rollers to follow the contours of the cam lobe as it is rotated to provide more uniform contact pressure against the workpiece.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.